Measurement of total mechanical loading on endothelial cells in vitro using micron -resolution particle image velocimetry

In the human vasculature, arteries respond and adapt to their mechanical environment through processes of tissue growth and remodeling. A key player in adaptation, endothelial cells, being situated between the vessel wall and the flowing blood, sense flow conditions and signal vessel change. This process, termed mechanotransduction, is the focus of intense investigation to uncover the role mechanical loading plays in triggering or abating vascular disease. Understanding fluid loading conditions on endothelial cells is paramount to this effort. This work addresses the need to determine the total hemodynamic loading on endothelial cells. A device was developed to simultaneously study flow and the endothelial cell response. For the first time, flow measurements have been performed over endothelial cells in vitro. From the subcellular-scale measurements, the cell surface topography was mapped and the complete stress tensor due to pressure and wall shear stress was determined. Pressure loading is established as a major contributor to the total hemodynamic loading condition. It is on the order of wall shear stress and significantly alters the direction of the principal stress. This work paves the way for studying the coupled problem of mechanical loading and biologic response of endothelial cells.